OBS / OBS Studio is pretty solid for (a completely free) screen capture software. It's reliable for a lot of different long-term uses if you want something to keep around after the jam.

OBS is technically intended for live streamers, but I've heard a lot of youtubers and whatnot use it for local recordings (I do as well). You just need to reduce the compression/etc. for a decent quality. (There are / should be plenty of tutorials for this around.)

While they're simpler to use, OBS is also a lot less resource-intensive on your computer than Fraps (free version limits record time), Bandicam (free version has watermarks), and CamStudio (only records to .avi/SWF), which are some free-ish alternatives. (I might be missing some?)